Zardnaar
Legend
I've never hit the issue. Making combats more difficult normally just takes better tactics, monsters that take advantage of environment, fight intelligently and don't attack in fireball formation, etc. In addition the DM decides how much XP to grant, I always discuss with my players how quickly they want to advance. The DM also has final say on optional rules, items and build options.
D&D shouldn't ever escalate to an arms race. If you feel like it is, work with your players to tone it down to something that works for everyone.
P.S. this advice is for anyone else reading this thread. No offense Z, but I know where you stand.
None taken its more form what I have observed with other DMs (not me). Inexperienced DMs the game tends to spiral out of control as they cant deal with it or the arms races starts. Myself I can deal with it in other ways and often be subtle about it.
For example say I have 2 PCs using the -5/+10 feats, one uses a bow the other uses a greatsword. The 3rd PC might use a weapon finesse battlemaster. A flaming shortsword might turn up in treasure, the greatsword user is luck to find a +1 weapon while the bow user gets some magical arrows or a magical +0 bow that glows in the dark. Something like the elemental weapons in PotA can also drop with things like weapon finesse +2 spears. Throwing a chain shirt on an ogre and not giving out more xp for it is also something I would do.
Although to be fair I want a featless game now interestingly the players also seem to be coming to this realisation (5E is to easy, well how bout we don't use feats). That or we might alternate 5E with other D&D's/clones or other games. If I am playing in a new group I tone things down or just play whatever the party needs.